To be unpickle-able, the code for f needs to be imported, which it can't be from the repl. Windows has this same issue, due to also not using fork().

From https://docs.python.org/3/library/pickle.html#what-can-be-pickled-and-unpickled: "Thus the defining module must be importable in the unpickling environment, and the module must contain the named object, otherwise an exception will be raised."

I'll wait a while to see who else chimes in, but I think this should be closed as "not a bug".